The political cartoon. At its best, sublime. A staple of the history classroom.
Over one hundred Clifford K. Berryman (1869-1949) political cartoons can be viewed and downloaded at the National Archives' Clifford K. Berryman Political Cartoon Collection. (I see that this has been on-line since 2008. New to me, though.) Berryman's lifelike political cartoons work great in courses on 20th century history:
The Center for Legislative Archives holds approximately 2,600 original pen-and-ink drawings by cartoonist Clifford K. Berryman in the U.S. Senate Collection. Berryman was one of Washington's best-known political cartoonists in the first half of the 20th century. Berryman drew for the Washington Post from 1890 until 1907, and then for the Washington Evening Star from 1907 until his death in 1949. Over one hundred of Berryman's cartoons are available for on-line viewing through the Archival Research Catalog by using the keyword Berryman.
As Berryman road off into the sunset, another Washington cartoonist was coming of age. Herb Block, "Herblock," (1909-2001) had a fast, bold line style. Nixon was a favorite target. Herblock's NYT obit noted: "He started drawing Nixon, who was usually depicted as shifty and grizzled, in 1948. Sometimes Nixon appeared as a vulture, other times as an undertaker, always as a man ready to benefit from the failure of others. But Mr. Block said he took no pleasure from the fact that the disgraced president was a cartoonist's dream. 'I didn't enjoy it,' he said, 'I really wanted him out.'" See the 2003 Library of Congress site, Herblock's History: Political Cartoons from the Crash to the Millennium, for an excellent survey of his work and for a number of medium to high resolution cartoons.
For earlier matieral, see Harpweek's World of Thomas Nast site; look for satirical prints from Puck Magazine, Harper's Weekly, and Frank Leslie's Illustrated on the Library of Congress Prints/Photos database; type "satirical" into the Beinecke Rare Books and MS Library search engine; or query the British Museums on-line archives for George Cruikshank, Thomas Rowlandson, Honoré Daumier, and others.